Flood probability increases as river projections rise again

April 5, 2013

The Souris River is now projected to attain at least minor flood stage at nearly every recording point from where the river enters North Dakota near Sherwood to where it exits the state near Westhope.

While the most recent Flood Potential Outlook issued Thursday by the National Weather Service raises the level of concern in a region that experienced damaging flood levels in 2011, there are no indications of a repeat of what occurred that year. Nevertheless, reaching minor flood stage or above is given a 90 percent chance of happening according to the latest NWS formulations.

The NWS categorizes flood levels as four stages action stage, minor flooding, moderate flooding and major flooding. Here are 90 percent probabilities for river levels along the Souris as issued by the NWS:

- Sherwood, 21.3 feet, moderate flood stage is 20 feet.

- Baker's Bridge, 14.6 feet, minor flood stage is 14 feet.

- Boy Scout Bridge, 16.1 feet, minor flood stage is 14 feet.

- Broadway Bridge, 1,546.7 feet, minor flood stage is 1,549 feet.

- Logan, 35.4 feet, minor flood stage is 34 feet.

- Sawyer, 24.1 feet, moderate flood stage is 24 feet.

- Velva, 1,505.7 feet, minor flood stage is 1,505 feet.

- Towner, 55.5 feet, moderate flood stage is 52 feet.

- Bantry, 13.3 feet, moderate flood stage is 11 feet.

The amount of water being released from three reservoirs on the Souris in Saskatchewan is slightly over 2,300 cubic feet per second. The Souris enters the north end of Lake Darling which is currently releasing 2,300 cfs.

"Our hope is that induced high water will be perfectly equal to what we see when the snowmelt is in full force," said Allen Schlag, NWS hydrologist in Bismarck.

According to the U.S. Army Corps of Engineers the intent is to draw down Lake Darling to 1,593 feet to make room for snowmelt runoff. Lake Darling was at 1,594.78 and falling late Thursday.

"When the local snowmelt starts, which you cannot control, you can cut down on Souris River flows out of Lake Darling," said Schlag.

The goal, says the Corps, is to not exceed a flow of 5,000 cfs at the Boy Scout Bridge west of Minot. The majority of Minot's dike system protects against approximately 7,000 cfs. Flows through the city in 2011 were estimated as high as 30,000 cfs.

The latest outlook cautions that this year's snowmelt is late, creating an enhanced risk of "minor and moderate definitions of flooding, but not much extra risk of reaching major flood stage."

In summary, the outlook issued late Thursday states: "Substantial increases in flow out of Rafferty, Boundary and Alameda Dams in Saskatchewan have prompted increased flows out of Lake Darling. These flows are making their way through the Souris River and are pushing an ice covered Souris to flood stage, or near flood stage, at all locations. So far there have been no ice related flood problems reported, but the higher water levels have increased the risk of ice related flooding."

In addition to increased flows forecast for the Souris, the NWS also upped projections for key tributaries on the Souris. The Des Lacs River, which joins the Souris at Burlington, is now given a 90 percent chance of reaching 13.2 feet, a one foot increase from earlier outlooks. Minor flood stage on the Des Lacs at Foxholm is 16 feet.

The outlook for the Wintering River near Karlsruhe has changed from a 90 percent chance of reaching 5.8 feet to a 90 percent chance of reaching 6.4 feet. Minor flood stage for the Wintering River is 7 feet.

Willow Creek, which flows out of the Turtle Mountains and joins the Souris at the J. Clark Salyer National Wildlife Refuge, is now given a 90 percent chance of reaching 13.5 feet. That compares with the March 21 outlook which projected 12.7 feet. Minor flood stage for Willow Creek is 10 feet.